The Third Generation Partnership Project (3GPP) unites six telecommunications standards bodies, known as “Organizational Partners,” and provides their members with a stable environment to produce the highly successful Reports and Specifications that define 3GPP technologies. A mobile device, also called a User Equipment (UE) or Mobile Station (MS), may operate in a wireless communication network that provides high-speed data and/or voice communications. The UE has access to mobile services via an Access Network (AN). The Access Network generally comprises a Radio Access Network (RAN) and a Core Network (CN).
There are different types of RANs, based on different types of Radio Access Technologies, such as for example: Global System for Mobile Communications (GSM)/General Packet Radio Service (GPRS) RAN (also called GERAN), Universal Mobile Telecommunication System (UMTS) RAN (also called UTRAN), Long-Term Evolution (LTE) RAN (also called E-UTRAN), Wireless Local Area Network (WLAN), WIMAX, . . . etc.
The wireless communication networks may implement circuit-switched (CS) and/or packet-switched (PS) communication protocols to provide various services. For example, the UE may operate in accordance with one or more of an Code Division Multiple Access (CDMA) networks, Time Division Multiple Access (TDMA) networks, Frequency Division Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA) networks, Single-Carrier FDMA (SC-FDMA) networks, etc. The terms “networks” and “systems” are often used interchangeably. A CDMA network may implement a radio technology such as Universal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA: includes Wideband-CDMA (W-CDMA) and Low Chip Rate (LCR) cdma2000 covers IS-2000, IS-95 and IS-856 standards. A TDMA network may implement a radio technology such as GSM. An OFDMA network may implement a radio technology such as Evolved UTRA (E-UTRA), IEEE 802.11, IEEE 802.16, IEEE 802.20, Flash-OFDM®, etc. UTRA, E-UTRA, and GSM are part of UMTS. LTE is a new release of UMTS that uses E-UTRA. UTRA, E-UTRA, GSM, UMTS and LTE are described in specification documents from 3GPP. These various radio technologies and standards are known in the art.
The Internet Protocol Multimedia Subsystem (IMS) as defined by 3GPP is an all-IP architecture for offering multimedia services. The main function of IMS is to set up media communication sessions between users, and between users and applications. IMS uses Session Initiation Protocol (SIP), Radius protocol, and/or Diameter protocol for initiating, modifying, and terminating an interactive user session that involves multimedia elements, such as call sessions, voicemail, call forwarding, instant messaging and online games. The IMS core network includes the Call Session Control Function (CSCF) and the Home Subscriber Server (HSS). IMS can be used to deliver Short Message Service (SMS) messages, using the technique known as SMS over generic IP access. A network node, the IP Short Message Gateway (IP-SM-GW), acts as an interface between the IMS and the network elements that handle SMS messages. To transmit an SMS message, the UE embeds the message into a SIP signaling message and sends it to the IMS core network. The IMS core network hands the message to the IP-SM-GW, which extracts the embedded SMS message and sends it to the SMS interworking Mobile Switching Center (SMS-IWMSC). The SMS-IWMSC then forwards the message to the SMS Service Center (SC), which is responsible for delivery of the message to its destination. In the reverse direction the SMS Service Center (SC) uses another network function, the Gateway Mobile Switching Center for Short Message Service (SMS-GMSC), is used to deliver the SMS message. Collectively the SMS-IWMSC, the SMS-GMSC, and the SMS Service Center are called an SMSC.